Uplink control information

ABSTRACT

Embodiments of the present disclosure relate to methods, devices, apparatuses and computer readable storage media for Uplink Control Information (UCI) design. The method comprises determining, at a terminal device, a matrix comprising a set of non-zero linear combination coefficients for quantizing a channel between the terminal device and a network device, the matrix having spatial components and frequency components; shifting the frequency components of the matrix circularly, such that a target coefficient of the set of non-zero linear combination coefficients is located in a frequency component with a predetermined index of the frequency components in a shifted matrix; generating a first indication indicating the spatial component associated with the target coefficient in the matrix; and transmitting, to the network device, uplink control information comprising the first indication. In this way, a new solution for designing the UCI may reduce the overhead for reporting the parameters in the UCI.

FIELD

Embodiments of the present disclosure generally relate to the field oftelecommunication and in particular, to methods, devices, apparatusesand computer readable storage media for Uplink Control Information (UCI)design.

BACKGROUND

In 3GPP New Radio (NR) Rel-15 and 16, a compression mechanism has beenintroduced to reduce the overhead in reporting Channel State Information(CSI) from UEs to the Base Transceiver Station (BTS), which is requiredto operate Multi-User Multiple Input Multiple Output (MU-MIMO) in thedownlink. The mechanism consists in two DFT-based operations in thespatial domain and in the frequency domain. These operations are appliedto each layer for rank indicators (RI) from 1 to 4. The CSI message maycomprise a Channel Quality Indicator (CQI) and a Precoding MatrixIndicator (PMI). The CQI may be obtained from an estimate of theexpected SINR after decoding of a codeword multiplexed across thereported spatial layers and PMI may comprise a set of complex-valuedprecoding weights that are needed to achieve that CQI. Both CQI and PMIparameters are reported per sub-band. The PMI is represented by a matrixfor each reported layer, each containing as many column vectors as thenumber of sub-bands. The SD and FD compression operations are applied tothese PMI matrices across their rows and columns respectively.

An important aspect of CSI signalling for MU-MIMO is the arrangement ofthe components of the compressed PMI in uplink control information (UCI)message. In a conventional way, this message may be organised in twoparts, namely “UCI part 1” and “UCI part 2”. The “UCI part 1” maycomprise the CQI information and the parameters needed to determine thepayload size of the “UCI part 2”. The “UCI part 1” transmitted in thePhysical Uplink Control Channel (PUCCH) may have a very short andfixed-size payload and may be encoded with very strong forward errorcorrection code to guarantee error-free decoding. The “UCI part 2” maycomprise the bulk of compressed PMI and be transmitted in the PhysicalUplink Shared Channel (PUSCH), hence it has the same error protection asdata.

SUMMARY

In general, example embodiments of the present disclosure provide asolution for Uplink Control Information (UCI) design.

In a first aspect, there is provided a method. The method comprisesdetermining, at a terminal device, a matrix comprising a set of non-zerolinear combination coefficients for quantizing a channel between theterminal device and a network device, the matrix having spatialcomponents and frequency components; shifting the frequency componentsof the matrix circularly, such that a target coefficient of the set ofnon-zero linear combination coefficients is located in a frequencycomponent with a predetermined index of the frequency components in ashifted matrix; generating a first indication indicating the spatialcomponent associated with the target coefficient in the matrix; andtransmitting, to the network device, uplink control informationcomprising the first indication.

In a second aspect, there is provided a method. The method comprisesreceiving, at a network device and from a terminal device, uplinkcontrol information comprising a first indication, the first indicationindicating spatial components associated with a target coefficient in amatrix comprising a set of non-zero linear combination coefficients forquantizing a channel between the terminal device and the network device,the matrix having the spatial components and frequency components; anddetermining state information of the channel based on the uplink controlinformation.

In a third aspect, there is provided a device. The device comprises atleast one processor; and at least one memory including computer programcodes; the at least one memory and the computer program codes areconfigured to, with the at least one processor, cause the device atleast to determine, at a terminal device, a matrix comprising a set ofnon-zero linear combination coefficients for quantizing a channelbetween the terminal device and a network device, the matrix havingspatial components and frequency components; shift the frequencycomponents of the matrix circularly, such that a target coefficient ofthe set of non-zero linear combination coefficients is located in afrequency component with a predetermined index of the frequencycomponents in a shifted matrix; generate a first indication indicatingthe spatial component associated with the target coefficient in thematrix; and transmit, to the network device, uplink control informationcomprising the first indication.

In a fourth aspect, there is provided a device. The device comprises atleast one processor; and at least one memory including computer programcodes; the at least one memory and the computer program codes areconfigured to, with the at least one processor, cause the device atleast to receive, at a network device and from a terminal device, uplinkcontrol information comprising a first indication, the first indicationindicating spatial components associated with a target coefficient in amatrix comprising a set of non-zero linear combination coefficients forquantizing a channel between the terminal device and the network device,the matrix having the spatial components and frequency components; anddetermine state information of the channel based on the uplink controlinformation.

In a fifth aspect, there is provided an apparatus comprises means fordetermining, at a terminal device, a matrix comprising a set of non-zerolinear combination coefficients for quantizing a channel between theterminal device and a network device, the matrix having spatialcomponents and frequency components; means for shifting the frequencycomponents of the matrix circularly, such that a target coefficient ofthe set of non-zero linear combination coefficients is located in afrequency component with a predetermined index of the frequencycomponents in a shifted matrix; means for generating a first indicationindicating the spatial component associated with the target coefficientin the matrix; and means for transmitting, to the network device, uplinkcontrol information comprising the first indication.

In a sixth aspect, there is provided an apparatus comprising means forreceiving, at a network device and from a terminal device, uplinkcontrol information comprising a first indication, the first indicationindicating spatial components associated with a target coefficient in amatrix comprising a set of non-zero linear combination coefficients forquantizing a channel between the terminal device and the network device,the matrix having the spatial components and frequency components; andmeans for determining state information of the channel based on theuplink control information.

In a seventh aspect, there is provided a computer readable medium havinga computer program stored thereon which, when executed by at least oneprocessor of a device, causes the device to carry out the methodaccording to the first aspect.

In an eighth aspect, there is provided a computer readable medium havinga computer program stored thereon which, when executed by at least oneprocessor of a device, causes the device to carry out the methodaccording to the second aspect.

It is to be understood that the summary section is not intended toidentify key or essential features of embodiments of the presentdisclosure, nor is it intended to be used to limit the scope of thepresent disclosure. Other features of the present disclosure will becomeeasily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to theaccompanying drawings, where:

FIG. 1 shows an example communication network in which exampleembodiments of the present disclosure may be implemented;

FIG. 2 shows a schematic diagram illustrating a process for UCI designaccording to example embodiments of the present disclosure;

FIGS. 3A and 3B show diagrams of an example matrix and the correspondingbitmap according to some example embodiments of the present disclosure;

FIGS. 4A and 4B show diagrams of an example matrix and the correspondingbitmap after the shifting operation according to some exampleembodiments of the present disclosure;

FIG. 5 shows a flowchart of an example method 500 of UCI designaccording to some example embodiments of the present disclosure;

FIG. 6 shows a flowchart of an example method 600 of UCI designaccording to some example embodiments of the present disclosure;

FIG. 7 is a simplified block diagram of a device that is suitable forimplementing example embodiments of the present disclosure; and

FIG. 8 illustrates a block diagram of an example computer readablemedium in accordance with some embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numeralsrepresent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with referenceto some example embodiments. It is to be understood that theseembodiments are described only for the purpose of illustration and helpthose skilled in the art to understand and implement the presentdisclosure, without suggesting any limitation as to the scope of thedisclosure. The disclosure described herein can be implemented invarious manners other than the ones described below.

In the following description and claims, unless defined otherwise, alltechnical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skills in the art to which thisdisclosure belongs.

As used herein, the term “communication network” refers to a networkthat follows any suitable communication standards or protocols such aslong term evolution (LTE), LTE-Advanced (LTE-A) and 5G NR, and employsany suitable communication technologies, including, for example,Multiple-Input Multiple-Output (MIMO), OFDM, time division multiplexing(TDM), frequency division multiplexing (FDM), code division multiplexing(CDM), Bluetooth, ZigBee, machine type communication (MTC), eMBB, mMTCand uRLLC technologies. For the purpose of discussion, In some exampleembodiments, the LTE network, the LTE-A network, the 5G NR network orany combination thereof is taken as an example of the communicationnetwork.

As used herein, the term “network device” refers to any suitable deviceat a network side of a communication network. The network device mayinclude any suitable device in an access network of the communicationnetwork, for example, including a base station (BS), a relay, an accesspoint (AP), a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a5G or next generation NodeB (gNB), a Remote Radio Module (RRU), a radioheader (RH), a remote radio head (RRH), a low power node such as afemto, a pico, and the like. For the purpose of discussion, in someexample embodiments, the gNB is taken as an example of the networkdevice.

The network device may also include any suitable device in a corenetwork, for example, including multi-standard radio (MSR) radioequipment such as MSR BSs, network controllers such as radio networkcontrollers (RNCs) or base station controllers (BSCs),Multi-cell/multicast Coordination Entities (MCEs), Mobile SwitchingCenters (MSCs) and MMEs, Operation and Management (O&M) nodes, OperationSupport System (OSS) nodes, Self-Organization Network (SON) nodes,positioning nodes, such as Enhanced Serving Mobile Position Centers(E-SMLCs), and/or Mobile Data Terminals (MDTs).

As used herein, the term “terminal device” refers to a device capableof, configured for, arranged for, and/or operable for communicationswith a network device or a further terminal device in a communicationnetwork. The communications may involve transmitting and/or receivingwireless signals using electromagnetic signals, radio waves, infraredsignals, and/or other types of signals suitable for conveyinginformation over air. In some example embodiments, the terminal devicemay be configured to transmit and/or receive information without directhuman interaction. For example, the terminal device may transmitinformation to the network device on predetermined schedules, whentriggered by an internal or external event, or in response to requestsfrom the network side.

Examples of the terminal device include, but are not limited to, userequipment (UE) such as smart phones, wireless-enabled tablet computers,laptop-embedded equipment (LEE), laptop-mounted equipment (LME), and/orwireless customer-premises equipment (CPE). For the purpose ofdiscussion, in the following, some embodiments will be described withreference to UEs as examples of the terminal devices, and the terms“terminal device” and “user equipment” (UE) may be used interchangeablyin the context of the present disclosure.

As used herein, the term “location server” may refer to a servicefunction which provides the positioning of the target UE to a locationclient. The location server may communicate with the target UE to obtainthe positioning measurement report from the target UE via a high layersignaling. The location service may also communicate with the networkdevice to obtain information associated with the positioning of thetarget UE. The location server may be a component independent of thenetwork device. As an option, the location server may be any functionmodule or function entity embedded in the network device.

Corresponding to the term “location server”, the term “location client”,as used herein, may refer to an application or entity which requests thelocation of the target UE. The location client may transmit a locationrequest to the location service and receives the positioning of thetarget UE from the location server. Also, the location client may beconsidered as the target UE itself.

As used herein, the term “cell” refers to an area covered by radiosignals transmitted by a network device. The terminal device within thecell may be served by the network device and access the communicationnetwork via the network device.

As used herein, the term “circuitry” may refer to one or more or all ofthe following:

(a) hardware-only circuit implementations (such as implementations inonly analog and/or digital circuitry) and(b) combinations of hardware circuits and software, such as (asapplicable): (i) a combination of analog and/or digital hardwarecircuit(s) with software/firmware and (ii) any portions of hardwareprocessor(s) with software (including digital signal processor(s)),software, and memory(ies) that work together to cause an apparatus, suchas a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s)or a portion of a microprocessor(s), that requires software (e.g.,firmware) for operation, but the software may not be present when it isnot needed for operation.

This definition of circuitry applies to all uses of this term in thisapplication, including in any claims. As a further example, as used inthis application, the term circuitry also covers an implementation ofmerely a hardware circuit or processor (or multiple processors) orportion of a hardware circuit or processor and its (or their)accompanying software and/or firmware. The term circuitry also covers,for example and if applicable to the particular claim element, abaseband integrated circuit or processor integrated circuit for a mobiledevice or a similar integrated circuit in server, a cellular networkdevice, or other computing or network device.

As used herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The term “includes” and its variants are to be read as openterms that mean “includes, but is not limited to”. The term “based on”is to be read as “based at least in part on”. The term “one embodiment”and “an embodiment” are to be read as “at least one embodiment”. Theterm “another embodiment” is to be read as “at least one otherembodiment”. Other definitions, explicit and implicit, may be includedbelow.

As described above, the Precoding Matrix Indicator (PMI) is representedby a matrix for each reported layer, each containing as many columnvectors as the number of sub-bands. The SD and FD compression operationsare applied to these PMI matrices across their rows and columnsrespectively. As a result, the PMI for a layer is compressed in threecomponent parts: an orthogonal basis set of DFT vectors for SDcompression, an orthogonal basis set of DFT vectors for FD compressionand a set of complex-valued linear combination (LC) coefficients.Therefore, both compression operations are linear projections on twoorthogonal bases. When the two orthogonal bases are reported byindicating a subset from a DFT-based codebook, the LC coefficients arequantized in amplitude and phase by using scalar quantizers. Becauseonly a subset of nonzero LC coefficients can be reported per layer toreduce overhead, both the location of the reported nonzero coefficientsand their complex values are required to be reported. A bitmap per layeris used to report these locations.

Each PMI vector can be reported to the BTS based on a complex (amplitudeand phase) scaling factor because this factor does not affect theprecoder design. This property is used, for example, to applyappropriate phase shifts to the columns of the PMI matrix before FDcompression to optimise the compression operation. This property alsoallows to apply a common scaling to all the LC coefficients beforequantization, such that they are upper-bounded in amplitude by 1 and thequantization interval for amplitude becomes [0,1].

This common scaling of LC coefficients is applied independently to thecoefficients of each layer and consists in the amplitude and phase ofthe “strongest” coefficient, i.e., the coefficient with the largestmagnitude, for that layer. Since the strongest coefficient afternormalization may equal to 1, neither amplitude nor phase for thestrongest coefficient are required to be reported. Instead, its locationin the bitmap is signalled by means of a strongest coefficient indicator(SCI).

An important aspect of Channel State Information (CSI) signalling forMulti-User Multiple Input Multiple Output (MU-MIMO) is the arrangementof the components of the compressed PMI in uplink control information(UCI) message. In a conventional way, this message may be organised intwo parts, namely “UCI part 1” and “UCI part 2”. The “UCI part 1” maycomprise the CQI information and the parameters needed to determine thepayload size of the “UCI part 2”. The “UCI part 1” transmitted in thePhysical Uplink Control Channel (PUCCH) may have a very short andfixed-size payload and may be encoded with very strong forward errorcorrection code to guarantee error-free decoding. The “UCI part 2” maycomprise the bulk of compressed PMI and be transmitted in the PhysicalUplink Shared Channel (PUSCH), hence it has the same error protection asdata.

The information in the “UCI part 1” that is used to determine thepayload size of “UCI part 2” can be arranged in two manners, namely (1)the number of the nonzero LC coefficients per each layer (the number ofthe layers equal to the maximum reported rank) and (2) the total numberof nonzero LC coefficients for all reported layers and the RI indicator.The both ways allow determining the reported rank and therefore numberof bitmaps in the “UCI part 2”. The number of the quantized coefficientsis also reported in the “UCI part 2”, from which the payload size can bedetermined.

Note that some parameters needed for determining the size of the “UCIpart 2” and for correct PMI decoding are not reported in “UCI part 1”because they are configured by the network. These are the parameterscontrolling the maximum overhead for CSI reporting, i.e., the size ofthe SD and FD bases and the maximum number of nonzero coefficients.

The manner (2), as mentioned above, is preferable, because the overheadfor indicating the number of nonzero LC coefficients in the “UCI part 1”may be significantly reduced. However, the manner (2) has a drawback ofmaking the signalling of the SCI more inefficient. In fact, there is oneSCI for each reported layer in part 2, because the normalization of theLC coefficients is done independently per layer. Unless a restriction isintroduced in the number of nonzero coefficients per layer, the SCIshould contain [log₂ N_(NZ)] bits, with N_(NZ) total number of nonzerocoefficients.

Introducing such a restriction is not desirable either because the UEshould select the LC coefficients to be reported to optimise thecompression jointly across the reported layers for a given maximumbudged of coefficients. Adding unnecessary constraints to thisoptimisation, for example by limiting the number of coefficients allowedto be reported per layer, may have a negative impact in performance.

Thus, the present disclosure proposes a signalling mechanism for theSCIs and the FD bases that reduces the overhead of the UCI message byexploiting a property of DFT-based frequency compression, namely thatany phase ramp applied across the columns of the LC coefficient matrixbefore FD compression is transparent to the BTS and does not requiresignalling.

Embodiments of the present disclosure provide a solution for UCI design,so as to at least in part solve the above and other potential problems.Some example embodiments of the present disclosure will be describedbelow with reference to the figures. However, those skilled in the artwould readily appreciate that the detailed description given herein withrespect to these figures is for explanatory purpose as the presentdisclosure extends beyond theses limited embodiments.

FIG. 1 shows an example communication network 100 in whichimplementations of the present disclosure can be implemented. Thecommunication network 100 includes a network device 110 and terminaldevices 120-1, 120-2 . . . and 120-N, which can be collectively orindividually referred to as “terminal device(s)” 120. The network 100can provide one or more cells 102 to serve the terminal device 120. Itis to be understood that the number of network devices, terminal devicesand/or cells is given for the purpose of illustration without suggestingany limitations to the present disclosure. The communication network 100may include any suitable number of network devices, terminal devicesand/or cells adapted for implementing implementations of the presentdisclosure.

In the communication network 100, the network device 110 can communicatedata and control information to the terminal device 120 and the terminaldevice 120 can also communication data and control information to thenetwork device 110. A link from the network device 110 to the terminaldevice 120 is referred to as a downlink (DL), while a link from theterminal device 120 to the network device 110 is referred to as anuplink (UL).

The communications in the network 100 may conform to any suitablestandards including, but not limited to, Global System for MobileCommunications (GSM), Long Term Evolution (LTE), LTE-Evolution,LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA),Code Division Multiple Access (CDMA), GSM EDGE Radio Access Network(GERAN), and the like. Furthermore, the communications may be performedaccording to any generation communication protocols either currentlyknown or to be developed in the future. Examples of the communicationprotocols include, but not limited to, the first generation (1G), thesecond generation (2G), 2.5G, 2.75G, the third generation (3G), thefourth generation (4G), 4.5G, the fifth generation (5G) communicationprotocols.

In order to obtain CSI of a communication channel between the networkdevice 110 and the terminal device 120, the network device 110 maytransmit a Channel State Information-reference signal (CSI-RS) to theterminal device 120. The terminal device 120 may receive the CSI-RS fromthe network device 110, and obtain channel information by measuring theCSI-RS. The terminal device 120 may then determine the CSI of thecommunication channel based on the obtained channel information and acorresponding codebook. For example, the obtained channel informationcan be quantized into the CSI based on the corresponding codebook. Theterminal device 120 may report the CSI to the network device 110. Theprocess for reporting the CSI is also called as “CSI feedback”. The CSImay ensure reliability of the wireless communication between the networkdevice 110 and the terminal device 120. As mentioned above, for the CSIsignalling, an important aspect is the arrangement of the components ofthe compressed PMI in uplink control information (UCI) message.

FIG. 2 shows a schematic diagram of a process 200 for the UCI designaccording to example embodiments of the present disclosure. For thepurpose of discussion, the process 200 will be described with referenceto FIG. 1. The process 200 may involve the terminal device 120 and thenetwork devices 110 as illustrated in FIG. 1.

As shown in FIG. 2, the terminal device 120 determines 210 a matrixcharacterizing a channel between the terminal device 120 and a networkdevice 110. The matrix may have spatial components and frequencycomponents and corresponding to a bitmap indicating a set of non-zerolinear combination coefficients for quantizing the channel.

In some example embodiments, the terminal device 120 may receive thedownlink control information received from the network device 110 andobtain a resource indication associate with the spatial components andthe frequency components, which is known for both terminal device andthe network device. The terminal device 120 may determine the matrixbased on the downlink control information and the resource indication.

Such matrix and the corresponding bitmap may be shown in FIG. 3A andFIG. 3B, respectively. As shown in FIG. 3A, the matrix has spatialcomponents in the spatial domain 310 and frequency components in thefrequency domain 320. Such matrix shown in FIG. 3A may be referred to asa LC coefficient matrix.

As mention above, the matrix may be obtained by applying the compressionto a PMI matrix representing the collection of precoding vectors for agiven spatial layer for all the configured sub-bands, which may beindicated in the downlink control information received from the networkdevice 110. Given the PMI matrix W of size 2N₁N₂×N₃, where N₁×N₂ is thenumber of antenna ports for each polarisation in the transmittwo-dimensional cross-polarised antenna array and N₃ is the number ofconfigured PMI sub-bands. For rank indicators (RI) larger than one,there is one such PMI matrix for each of the RI spatial layers. Thecompression operations on PMI matrix W are linear and can be representedby the following equation:

W=W ₁ {tilde over (W)} ₂ W _(f) ^(H)  (1)

where the column vectors of matrix W₁ are the components of the SDorthogonal basis of size 2L, the columns of W_(f) form the FD orthogonalbasis of size M, and {tilde over (W)}₂ is a 2L×M matrix ofcomplex-valued LC coefficients. The matrix {tilde over (W)}₂ may referto the matrix shown in FIG. 3A. To further reduce the signallingoverhead, only a subset of the 2LM LC coefficients are reported, and theremaining ones are set to zero. This group of reported LC coefficientsare referred to as non-zero (NZ) coefficients. The NZ coefficient mayrefer to the cells in FIG. 3A which are not equal to zero, for example,the cell 331.

Thus, the PMI report for a layer may consists of two indicators for theSD and FD basis subset selection, respectively and a 2L×M bitmapindicating the location of the K_(NZ) nonzero coefficients in the {tildeover (W)}₂ matrix. The bitmap corresponding to the W₂ matrix may beshown in FIG. 3B. As shown in FIGS. 3A and 3B, the row and column of thebitmap may corresponding to the spatial components and the frequencycomponents, for example, the 0^(th) frequency component in the frequencydomain 320 corresponds to the 0^(th) column of the bitmap.

There is the target coefficient in the K_(NZ) nonzero coefficients inthe {tilde over (W)}₂ matrix. The target coefficient may be referred toas the maximum coefficient of the non-zero coefficients, i.e. thestrongest coefficient. In order to reducing the overhead for reportingthe indication for strongest coefficient, the terminal device 120determines shifting operation for the frequency components of thematrix, such that the strongest coefficient is located in a frequencycomponent with a predetermined index.

In some example embodiments, the terminal device 120 may determineindices of the frequency components and perform modulo operation for thefrequency components in the matrix based on the indices of the frequencycomponents, the number of the frequency components in a predefined setof frequency components, the predetermined index and a reference indexof the frequency component. The reference index may indicate frequencycomponent associated with the target coefficient before shifting. Theterminal device 120 may perform the shifting operation based on resultof the modulo operation.

For example, let N₃ is the number of frequency components, M<N₃ the sizeof the frequency domain basis formed by frequency components withindices m₀, m₁, . . . , m_(M-1), and m_(i) _(max) is the index of thefrequency component with the strongest coefficient. For example,assuming that the predefined index value for the component m_(i) _(max)is 0. The terminal device 120 may perform the shifting operation basedon the following equation:

{m _(i)}→{(m _(i) −m _(i) _(max) )mod N ₃}  (2)

Then, the terminal device 120 determines an indication for the strongestcoefficient, i.e. the SCI, based on the spatial components where thestrongest coefficient located. The SCI may indicate the spatialcomponent associated with the target coefficient in the matrix.

The terminal device 120 further generates another indication forindicating a frequency range associated with a subset of the frequencycomponents based on the based on the predetermined index and thefrequency components. That is, the subset of the frequency componentsexcludes the frequency component with the predetermined index.

In some example embodiments, the terminal device 120 may determine, fromthe frequency components, a target frequency component associated withthe predetermined index and select from the frequency components, thesubset of the frequency components excluding the target frequencycomponent. The terminal device 120 may determine the indices of thesubset of the frequency components and generate the indication forindicating the frequency range based on the indices of the subset of thefrequency component.

Referring back to the assumption related to the equation (2), theterminal device 120 may report the subset of the frequency components ofsize M−1, without the “0^(th)” frequency component as below:

(m _(i) _(max) ₊₁ −m _(i) _(max) )mod N ₃,(m _(i) _(max) ₊₂ −m _(i)_(max) )mod N ₃, . . . ,(m _(i) _(max−1) −m _(i) _(max) )mod N ₃  (3)

After determining the SCI and the indication associated with thefrequency range, the terminal device 120 may transmit 220 the uplinkcontrol information comprising both of the indications to the networkdevice 110.

It should be understood that the UCI may comprise other necessarymessage for reporting the related parameters for estimating the channelstate.

In some example embodiments, the UCI may also comprise a bitmapcorresponding to the matrix of the LC coefficient. A bitmap may bedetermined based on the matrix before the shifting operation. Asmentioned above, such bitmap may indicate the locations of the NZcoefficient in the matrix. After the shifting operation of the matrix,the bitmap may also be updated based on the predetermined index.

In some example embodiments, the terminal device 120 may determine acorresponding relationship between the predetermined index and eachindex of the indices of the frequency components based on the indices ofthe frequency components and the predetermined index and update thebitmap based on the corresponding relationship.

In some example embodiments, the terminal device 120 transmits theuplink control information also comprising the updated bitmap.

With reference to FIGS. 3A-3B and FIGS. 4A-4B, the shifting operationmay be shown clearly. As mention above the matrix of FIG. 3A may have asize of 2L*M, there are a set of NZ coefficients in the matrix and FIG.3B shows a bitmap corresponding to the matrix of FIG. 3A. As shown inFIG. 3A, assuming the strongest coefficient 330 is located in the 1^(th)frequency component 341. For example, the terminal device 120 may shiftthe matrix such that the strongest coefficient is located in the 0^(th)frequency component. The shifted matrix may be shown in FIG. 4A. Thestrongest coefficient 330 is located in the 0^(th) frequency component340. Correspondingly, the bitmap shown in FIG. 3B may be updated to bethe bitmap shown in FIG. 4B.

If we assume, without loss of generality, a row-wise reading order ofthe bitmap in FIG. 4A, the strongest coefficient is the third NZcoefficient, hence, without the proposal of the present disclosure, itwould be indicated with └ log₂ K_(NZ)┐=4 bits: SCI=2 or 0010 (4-bitbinary representation of 2). The value K_(NZ)=10 for this layer shouldalso be reported in “UCI part 1”.

According to the solution of the present disclosure, if thepredetermined index is “0th”, the terminal device 120 may apply theshift operation to the frequency components of one position to the left,in the example of FIG. 3A. For example, let us assume the frequencycomponents are {m₀, m₁, . . . , m_(M-1)}={0,1,3,5,10,11,12} with theindex of the FD component with the strongest coefficient given by m_(i)_(max) =1. After the circular shift and re-ordering the FD basis subsetis given by {0,2,4,9,10,11,12}. On the other hand, the SCI is indicatedwith ┌log₂ 2L┐=3 bits reporting the SD component index, which in theexample is: SCI=1 or 001 (3-bit binary representation of 1).

Referring FIG. 2 again, the network device 110 receives the uplinkcontrol information from the terminal device 120 and determines stateinformation of the channel based on the uplink control information.

In some example embodiments, the network device 110 may determine thematrix based on the uplink control information and determine the stateinformation based on the matrix. As mentioned above, the matrix may beobtained by apply the compression of the PMI matrix. The network device110 needs to reconstruct the PMI matrix based on the matrix. Accordingto the UCI, the network device 110 may determine the subset of thefrequency components excluding the target frequency component and thenetwork device 110 may reconstruct the PMI by adding the targetfrequency component to the subset of the frequency components.

In this way, a new solution for designing the UCI may reduce theoverhead for reporting the parameters in the “UCI part 1” and “UCI part2”.

In the following, the principle for circular shift will be explained. Asmention above, any circular shift applied to the frequency components isequivalent to a multiplication of the columns of the PMI by a phase rampbefore applying frequency compression. Such phase ramp operationperformed at the terminal device 120 does not need to be reported to thenetwork device 110 because it is transparent to the precoder design.

It is well known that a phase rotation across the columns of a precodingmatrix W does not affect the precoder performance, hence the networkdevice 110 may reconstruct W up to a phase adjustment per column withoutaffecting performance. This is true for any type of precoder design. Itwill be shown that phase adjustments applied across the columns ofmatrix W₂ before frequency domain compression do not need to be reportedto the network device 110. It will also be pointed out that the choiceof these phases is an important degree of freedom that a terminal device120 can exploit to improve frequency compression, i.e. reduce thereconstruction error at the network device 110.

At first, considering an ideal case for frequency compression, withoutbasis subset selection, i.e. assuming that M=N₃, and with reporting ofall 2LN₃ unquantized frequency domain coefficients. Note that this isjust a hypothetical case as there is no actual compression gain in thefrequency domain. Assuming that a terminal device 120 applies phaseadjustments on the columns of W₂ before the DFT processing across thesub-bands and we indicate with R a diagonal matrix of arbitrary phaserotations:

{tilde over (W)} ₂ =W ₂ RW _(f)  (4)

If the network device 110 knows R, the precoder W is reconstructed as:

W(R)=W ₁ {tilde over (W)} ₂(RW _(f))^(H) =W ₁ W ₂  (5)

whereas, if the network device 110 is unaware of R, the reconstructionyields:

W=W ₁ {tilde over (W)} ₂ W _(f) ^(H) =W ₁ W ₂ R  (6)

In this ideal case, we observe that 1) the difference between thereconstruction (5) and (6) is just a phase rotation across theprecoder's columns, i.e.

W=W(R)R  (7)

and 2) assuming perfect reporting of the 2L×N₃ linear combination matrixW₂, applying the phase rotations in (4) is irrelevant.

Considering the realistic case of basis subset selection with M≤N₃ andquantization of the linear combination coefficients and say {tilde over(W)}′₂ is the 2L×N₃ matrix of FD coefficients known at the networkdevice 110. Note that only up to K₀ coefficients of {tilde over (W)}′₂are nonzero. Quantisation error also affects the nonzero coefficients.Introducing the error matrix between the realistic and ideal matrix oflinear combination coefficients:

E={tilde over (W)}′ ₂ −{tilde over (W)} ₂  (8)

Such that {tilde over (W)}′₂ can be expressed, in a very general case,as:

{tilde over (W)}′ ₂ ={tilde over (W)} ₂ +E=W ₂ RW _(f) +E  (9)

If the network device 110 knows the phase shifts R, the precoder W′ isreconstructed, with error, as:

W′(R)=W ₁ {tilde over (W)}′ ₂(RW _(f))^(H) =W ₁(W ₂ RW _(f) +E)W _(f)^(H) R ^(H) =W ₁ W ₂ +W ₁ EW _(f) ^(H) R ^(H)  (10)

If the network device 110 is unaware of R, the precoder reconstructionyields:

W′=W ₁ {tilde over (W)}′ ₂ W _(f) ^(H) W ₁(W ₂ RW _(f) +E)W _(f) ^(H) =W₁ W ₂ R+W ₁ EW _(f) ^(H)  (11)

By comparing (10) and (11), it will have:

W′=W′(R)R  (12)

i.e., the difference between the two reconstructions, with and withoutreporting of R, is a phase rotation applied to the precoder's columns,which does not affect the precoder's performance. However, unlike in theideal case, applying appropriate phase rotations at the terminal devicedoes make a difference in terms of reconstruction error. In fact, theterminal device may optimise the selection of the phase rotations R suchthat the reconstruction error E is minimised according to some metric,even if the network device is unaware of these phase adjustments.

Note that both results (7) and (12) hold when W_(f) is 2L×M, instead of2L×N₃, but the expressions for W′ and W′ (R) are more complicatedbecause W_(f)W_(f) ^(H) is no longer the identity matrix.

In conclusion, when applying frequency domain compression, optimisationof the phase adjustments R can be used by the terminal device to improvethe PMI accuracy. However, these adjustments do not need to becommunicated to the network device to achieve this gain.

Note that several operations can be expressed by these phase rotations.An oversampled DFT codebook can be described as the union of O₃circularly shifted versions of a critically sampled codebook, where theminimum shift is fractional. Accordingly, we can express the selectionof one of the O₃ orthogonal groups of size N₃ by using notation (3) withR given by the phase ramp:

$\begin{matrix}{R_{o} = \begin{pmatrix}1 & 0 & 0 & 0 & 0 \\0 & e^{j2\pi \frac{k}{O_{3}N_{3}}} & 0 & 0 & 0 \\0 & 0 & e^{j2\pi \frac{2k}{O_{3}N_{3}}} & 0 & 0 \\0 & 0 & 0 & \ddots & 0 \\0 & 0 & 0 & 0 & e^{j2\pi \frac{{({N_{3} - 1})}k}{O_{3}N_{3}}}\end{pmatrix}} & (13)\end{matrix}$

and k∈[0, . . . , O₃−1]. Similarly, a circular shift of the N₃ frequencydomain candidate components can be obtained by applying a phase rampacross the columns of W₂, in the original domain, with minimum shiftmultiple of O₃. For example, a circular shift that moves FD component ofindex n to position ‘0’ can be expressed by (4) with R given by thephase ramp:

$\begin{matrix}{R_{s} = \begin{pmatrix}1 & 0 & 0 & 0 & 0 \\0 & e^{j2\pi \frac{n}{N_{3}}} & 0 & 0 & 0 \\0 & 0 & e^{j2\pi \frac{2n}{N_{3}}} & 0 & 0 \\0 & 0 & 0 & \ddots & 0 \\0 & 0 & 0 & 0 & e^{j2\pi \frac{{({N_{3} - 1})}n}{N_{3}}}\end{pmatrix}} & (14)\end{matrix}$

and n∈[0, . . . , N₃−1]. Finally, oversampling and circular shifts canalso be combined with phase adjustments on the columns of W₂ to ensuresmooth phase transitions along its rows before applying frequency domaincompression and avoid ‘phase jumps’. Denoting the diagonal matrix ofthese phase adjustments as R_(ϕ):

$\begin{matrix}{R_{\varphi} = \begin{pmatrix}e^{j\varphi_{0}} & 0 & 0 & 0 & 0 \\0 & e^{j\varphi_{1}} & 0 & 0 & 0 \\0 & 0 & e^{j\varphi_{2}} & 0 & 0 \\0 & 0 & 0 & \ddots & 0 \\0 & 0 & 0 & 0 & e^{j\varphi_{N_{3} - 1}}\end{pmatrix}} & (15)\end{matrix}$

with ϕ_(n)∈[0,2π). In general, a terminal device can apply a combinationof these three operations (oversampling, circular shifts, phaseadjustments) by performing a set of phase rotations on the columns ofW₂, as described in (4), with a rotation matrix given by:

$\begin{matrix}{R = {{R_{o}R_{s}R_{\varphi}} = \begin{pmatrix}e^{j\varphi_{0}} & 0 & 0 & 0 & 0 \\0 & e^{j{({{2\pi \frac{{O_{3}n} + k}{O_{3}N_{3}}} + \varphi_{1}})}} & 0 & 0 & 0 \\0 & 0 & e^{j{({{2\pi \frac{2{({{O_{3}n} + k})}}{O_{3}N_{3}}} + \varphi_{2}})}} & 0 & 0 \\0 & 0 & 0 & \ddots & 0 \\0 & 0 & 0 & 0 & e^{j{({{2\pi \frac{{({N_{3} - 1})}{({{O_{3}n} + k})}}{O_{3}N_{3}}} + \varphi_{N_{3} - 1}})}}\end{pmatrix}}} & (16)\end{matrix}$

More details of the example embodiments in accordance with the presentdisclosure will be described with reference to FIGS. 5-6.

FIG. 5 shows a flowchart of an example method 500 for UCI designaccording to some example embodiments of the present disclosure. Themethod 500 can be implemented at the terminal device 120 as shown inFIG. 1. For the purpose of discussion, the method 500 will be describedwith reference to FIG. 1.

At 510, the terminal device 110 determines a matrix comprising a set ofnon-zero linear combination coefficients for quantizing a channelbetween the terminal device and a network device, the matrix havingspatial components and frequency components.

In some example embodiments, the terminal device 110 may receivedownlink control information received from the network device and obtaina resource indication associate with the spatial components and thefrequency components. The terminal device 110 may also determine thematrix based on the downlink control information and the resourceindication.

At 520, the terminal device 110 shifts the frequency components of thematrix circularly, such that a target coefficient of the set of non-zerolinear combination coefficients is located in a frequency component witha predetermined index of the frequency components in a shifted matrix.

In some example embodiments, the terminal device 110 may determineindices of the frequency components. The terminal device 110 may alsodetermine a reference index from the indices of the frequencycomponents, the reference index indicating a frequency componentassociated with the target coefficient in the matrix and shift thefrequency components based on the indices of the frequency components,the predetermined index and the reference index.

At 530, the terminal device 110 generates a first indication indicatingthe spatial component associated with the target coefficient in thematrix.

In some example embodiments, the terminal device 110 may determine, asthe target coefficient, a maximum coefficient from the set of non-zerolinear combination coefficients and generate the first indication basedon the index of the spatial component associated with the targetcoefficient in the matrix.

At 540, the terminal device 110 transmits, to the network device 120,uplink control information comprising the first indication.

In some example embodiments, the terminal device 110 may determine,based on the shifted matrix, a bitmap indicating locations of thenon-zero linear combination coefficients in the shifted matrix; andtransmit the uplink control information comprising the bitmap.

In some example embodiments, the terminal device 110 may generate, basedon the predetermined index and the frequency components, a secondindication indicating a frequency range associated with a subset of thefrequency components and transmit the uplink control informationcomprising the second indication.

In some example embodiments, the terminal device 110 may determine, fromthe frequency components, a target frequency component associated withthe predetermined index and select, from the frequency components, thesubset of the frequency components excluding the target frequencycomponent. The terminal device 110 may also determine indices of thesubset of the frequency components after the shifting and generate thesecond indication based on the indices of the subset of the frequencycomponent

FIG. 6 shows a flowchart of an example method 600 for UCI designaccording to some example embodiments of the present disclosure. Themethod 600 can be implemented at the network device 110 as shown inFIG. 1. For the purpose of discussion, the method 600 will be describedwith reference to FIG. 1.

At 610, the network device 110 receives at a network device and from aterminal device 120, uplink control information comprising a firstindication, the first indication indicating spatial componentsassociated with a target coefficient in a matrix comprising a set ofnon-zero linear combination coefficients for quantizing a channelbetween the terminal device and the network device, the matrix havingthe spatial components and frequency components.

At 620, the network device 110 determines state information of thechannel based on the uplink control information.

In some example embodiments, the network device 110 may determine thematrix based on the uplink control information and determine the stateinformation based on the matrix.

In some example embodiments, the network device 110 may receive uplinkcontrol information comprising the uplink control information comprisingthe bitmap indicating locations of the non-zero linear combinationcoefficients in a shifted matrix obtained by shifting the frequencycomponents of the matrix circularly.

In some example embodiments, the network device 110 may receive uplinkcontrol information comprising the second indication indicating afrequency range associated with a subset of the frequency components.

In some example embodiments, an apparatus capable of performing themethod 500 (for example, implemented at the terminal device 110) maycomprise means for performing the respective steps of the method 500.The means may be implemented in any suitable form. For example, themeans may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means fordetermining, at a terminal device, a matrix comprising a set of non-zerolinear combination coefficients for quantizing a channel between theterminal device and a network device, the matrix having spatialcomponents and frequency components; means for shifting the frequencycomponents of the matrixcircularly, such that a target coefficient ofthe set of non-zero linear combination coefficients is located in afrequency component with a predetermined index of the frequencycomponents in a shifted matrix; means for generating a first indicationindicating the spatial component associated with the target coefficientin the matrix; and means for transmitting, to the network device, uplinkcontrol information comprising the first indication.

In some example embodiments, an apparatus capable of performing themethod 600 (for example, implemented at the network device 120) maycomprise means for performing the respective steps of the method 600.The means may be implemented in any suitable form. For example, themeans may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means forreceiving, at a network device and from a terminal device, uplinkcontrol information comprising a first indication, the first indicationindicating spatial components associated with a target coefficient in amatrix comprising a set of non-zero linear combination coefficients forquantizing a channel between the terminal device and the network device,the matrix having the spatial components and frequency components andmeans for determining state information of the channel based on theuplink control information.

FIG. 7 is a simplified block diagram of a device 700 that is suitablefor implementing embodiments of the present disclosure. The device 700may be provided to implement the communication device, for example theterminal device 120 and the network device 110 as shown in FIG. 1. Asshown, the device 700 includes one or more processors 710, one or morememories 740 coupled to the processor 710, and one or more transmittersand/or receivers (TX/RX) 740 coupled to the processor 710.

The TX/RX 740 is for bidirectional communications. The TX/RX 740 has atleast one antenna to facilitate communication. The communicationinterface may represent any interface that is necessary forcommunication with other network elements.

The processor 710 may be of any type suitable to the local technicalnetwork and may include one or more of the following: general purposecomputers, special purpose computers, microprocessors, digital signalprocessors (DSPs) and processors based on multicore processorarchitecture, as non-limiting examples. The device 700 may have multipleprocessors, such as an application specific integrated circuit chip thatis slaved in time to a clock which synchronizes the main processor.

The memory 720 may include one or more non-volatile memories and one ormore volatile memories. Examples of the non-volatile memories include,but are not limited to, a Read Only Memory (ROM) 724, an electricallyprogrammable read only memory (EPROM), a flash memory, a hard disk, acompact disc (CD), a digital video disk (DVD), and other magneticstorage and/or optical storage. Examples of the volatile memoriesinclude, but are not limited to, a random access memory (RAM) 722 andother volatile memories that will not last in the power-down duration.

A computer program 730 includes computer executable instructions thatare executed by the associated processor 710. The program 730 may bestored in the ROM 1020. The processor 710 may perform any suitableactions and processing by loading the program 730 into the RAM 720.

The embodiments of the present disclosure may be implemented by means ofthe program 730 so that the device 700 may perform any process of thedisclosure as discussed with reference to FIGS. 2 to 4. The embodimentsof the present disclosure may also be implemented by hardware or by acombination of software and hardware.

In some embodiments, the program 730 may be tangibly contained in acomputer readable medium which may be included in the device 700 (suchas in the memory 720) or other storage devices that are accessible bythe device 700. The device 700 may load the program 730 from thecomputer readable medium to the RAM 722 for execution. The computerreadable medium may include any types of tangible non-volatile storage,such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like.FIG. 8 shows an example of the computer readable medium 800 in form ofCD or DVD. The computer readable medium has the program 730 storedthereon.

Generally, various embodiments of the present disclosure may beimplemented in hardware or special purpose circuits, software, logic orany combination thereof. Some aspects may be implemented in hardware,while other aspects may be implemented in firmware or software which maybe executed by a controller, microprocessor or other computing device.While various aspects of embodiments of the present disclosure areillustrated and described as block diagrams, flowcharts, or using someother pictorial representations, it is to be understood that the block,apparatus, system, technique or method described herein may beimplemented in, as non-limiting examples, hardware, software, firmware,special purpose circuits or logic, general purpose hardware orcontroller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer programproduct tangibly stored on a non-transitory computer readable storagemedium. The computer program product includes computer-executableinstructions, such as those included in program modules, being executedin a device on a target real or virtual processor, to carry out themethods 500 and 600 as described above with reference to FIGS. 2-4.Generally, program modules include routines, programs, libraries,objects, classes, components, data structures, or the like that performparticular tasks or implement particular abstract data types. Thefunctionality of the program modules may be combined or split betweenprogram modules as desired in various embodiments. Machine-executableinstructions for program modules may be executed within a local ordistributed device. In a distributed device, program modules may belocated in both local and remote storage media.

Program code for carrying out methods of the present disclosure may bewritten in any combination of one or more programming languages. Theseprogram codes may be provided to a processor or controller of a generalpurpose computer, special purpose computer, or other programmable dataprocessing apparatus, such that the program codes, when executed by theprocessor or controller, cause the functions/operations specified in theflowcharts and/or block diagrams to be implemented. The program code mayexecute entirely on a machine, partly on the machine, as a stand-alonesoftware package, partly on the machine and partly on a remote machineor entirely on the remote machine or server.

In the context of the present disclosure, the computer program codes orrelated data may be carried by any suitable carrier to enable thedevice, apparatus or processor to perform various processes andoperations as described above. Examples of the carrier include a signal,computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium ora computer readable storage medium. A computer readable medium mayinclude but not limited to an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, ordevice, or any suitable combination of the foregoing. More specificexamples of the computer readable storage medium would include anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing.

Further, while operations are depicted in a particular order, thisshould not be understood as requiring that such operations be performedin the particular order shown or in sequential order, or that allillustrated operations be performed, to achieve desirable results. Incertain circumstances, multitasking and parallel processing may beadvantageous. Likewise, while several specific implementation detailsare contained in the above discussions, these should not be construed aslimitations on the scope of the present disclosure, but rather asdescriptions of features that may be specific to particular embodiments.Certain features that are described in the context of separateembodiments may also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment may also be implemented in multipleembodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specificto structural features and/or methodological acts, it is to beunderstood that the present disclosure defined in the appended claims isnot necessarily limited to the specific features or acts describedabove. Rather, the specific features and acts described above aredisclosed as example forms of implementing the claims.

What is claimed is:
 1. A method, comprising: determining, at a terminaldevice, a matrix comprising a set of non-zero linear combinationcoefficients for quantizing a channel between the terminal device and anetwork device, the matrix having spatial components and frequencycomponents; shifting the frequency components of the matrix circularly,such that a target coefficient of the set of non-zero linear combinationcoefficients is located in a frequency component with a predeterminedindex of the frequency components in a shifted matrix; generating afirst indication indicating the spatial component associated with thetarget coefficient in the matrix; and transmitting, to the networkdevice, uplink control information comprising the first indication. 2.The method of claim 1, wherein determining the matrix comprises:receiving downlink control information received from the network device;obtaining a resource indication associate with the spatial componentsand the frequency components; and determining the matrix based on thedownlink control information and the resource indication.
 3. The methodof claim 1, wherein shifting the frequency components comprises:determining indices of the frequency components; determining a referenceindex from the indices of the frequency components, the reference indexindicating a frequency component associated with the target coefficientin the matrix; shifting the frequency components based on the indices ofthe frequency components, the predetermined index and the referenceindex.
 4. The method of claim 1, wherein generating the first indicationcomprises: determining, as the target coefficient, a maximum coefficientfrom the set of non-zero linear combination coefficients; and generatingthe first indication based on the index of the spatial componentassociated with the target coefficient in the matrix.
 5. The method ofclaim 1, further comprising: determining, based on the shifted matrix, abitmap indicating locations of the non-zero linear combinationcoefficients in the shifted matrix; and transmitting the uplink controlinformation comprising the bitmap.
 6. The method of claim 1, furthercomprising: generating, based on the predetermined index and thefrequency components, a second indication indicating a frequency rangeassociated with a subset of the frequency components; transmitting theuplink control information comprising the second indication.
 7. Themethod of claim 6, wherein generating the second indication comprises:determining, from the frequency components, a target frequency componentassociated with the predetermined index; selecting, from the frequencycomponents, the subset of the frequency components excluding the targetfrequency component; determining indices of the subset of the frequencycomponents after the shifting; and generating the second indicationbased on the indices of the subset of the frequency component.
 8. Amethod, comprising: receiving, at a network device and from a terminaldevice, uplink control information comprising a first indication, thefirst indication indicating spatial components associated with a targetcoefficient in a matrix comprising a set of non-zero linear combinationcoefficients for quantizing a channel between the terminal device andthe network device, the matrix having the spatial components andfrequency components; and determining state information of the channelbased on the uplink control information, the uplink control informationcomprising a bitmap indicating locations of the non-zero linearcombination coefficients in a shifted matrix obtained by shifting thefrequency components of the matrix circularly.
 9. The method of claim 8,wherein determining the state information comprises: determining thematrix based on the uplink control information; and determining thestate information based on the matrix.
 10. The method of claim 8,further comprising: receiving uplink control information comprising thesecond indication indicating a frequency range associated with a subsetof the frequency components.
 11. A device, comprising: at least oneprocessor; and at least one memory including computer program codes; theat least one memory and the computer program codes are configured to,with the at least one processor, cause the device at least to:determine, at a terminal device, a matrix comprising a set of non-zerolinear combination coefficients for quantizing a channel between theterminal device and a network device, the matrix having spatialcomponents and frequency components; shift the frequency components ofthe matrix circularly, such that a target coefficient of the set ofnon-zero linear combination coefficients is located in a frequencycomponent with a predetermined index of the frequency components in ashifted matrix; generate a first indication indicating the spatialcomponent associated with the target coefficient in the matrix; andtransmit, to the network device, uplink control information comprisingthe first indication.
 12. The device of claim 11, the device is causedto determine the matrix by: receiving downlink control informationreceived from the network device; obtaining a resource indicationassociate with the spatial components and the frequency components; anddetermining the matrix based on the downlink control information and theresource indication.
 13. The device of claim 11, the device is caused toshift the frequency components by: determining indices of the frequencycomponents; determining a reference index from the indices of thefrequency components, the reference index indicating a frequencycomponent associated with the target coefficient in the matrix; shiftingthe frequency components based on the indices of the frequencycomponents, the predetermined index and the reference index.
 14. Thedevice of claim 11, the device is caused to generate the firstindication by: determining, as the target coefficient, a maximumcoefficient from the set of non-zero linear combination coefficients;and generating the first indication based on the index of the spatialcomponent associated with the target coefficient in the matrix.
 15. Thedevice of claim 11, the device is further caused to: determine, based onthe shifted matrix, a bitmap indicating locations of the non-zero linearcombination coefficients in the shifted matrix; and transmit the uplinkcontrol information comprising the bitmap.
 16. The device of claim 11,the device is further caused to: generate, based on the predeterminedindex and the frequency components, a second indication indicating afrequency range associated with a subset of the frequency components;transmit the uplink control information comprising the secondindication.
 17. The device of claim 16, the device is caused to generatethe second indication by: determining, from the frequency components, atarget frequency component associated with the predetermined index;selecting, from the frequency components, the subset of the frequencycomponents excluding the target frequency component; determining indicesof the subset of the frequency components after shifting; and generatingthe second indication based on the indices of the subset of thefrequency component.
 18. A device, comprising: at least one processor;and at least one memory including computer program codes; the at leastone memory and the computer program codes are configured to, with the atleast one processor, cause the device at least to: receive, at a networkdevice and from a terminal device, uplink control information comprisinga first indication, the first indication indicating spatial componentsassociated with a target coefficient in a matrix comprising a set ofnon-zero linear combination coefficients for quantizing a channelbetween the terminal device and the network device, the matrix havingthe spatial components and frequency components; and determine stateinformation of the channel based on the uplink control information, theuplink control information comprising a bitmap indicating locations ofthe non-zero linear combination coefficients in a shifted matrixobtained by shifting the frequency components of the matrix circularly.19. The device of claim 18, the device is caused to determine the stateinformation by: determining the matrix based on the uplink controlinformation; and determining the state information based on the matrix.20. The device of claim 18, the device is further caused to: receiveuplink control information comprising the second indication indicating afrequency range associated with a subset of the frequency components.21. A non-transitory computer readable medium comprising programinstructions for causing an apparatus to perform at least the method ofclaim
 1. 22. A non-transitory computer readable medium comprisingprogram instructions for causing an apparatus to perform at least themethod of claim 8.